Tagged Questions

The photon is the quantum of the electromagnetic four-potential, and therefore the massless bosonic particle associated with the electromagnetic force, commonly also called the "particle of light". Use this tag for questions about the quantum-mechanical understanding of light and/or electromagnetic ...

I'm curious about how the material absorb the light and reflect the light back as colors in a sense of Quantum Mechanics (Quantum Electro Dynamics)
Does Hadron related to the absorbs of photon ? or ...

When some photon detector detects a photon, is it an instantaneous process (because a photon can be thought of as a point particle), or does the detection require a finite amount of time depending on ...

Photons are considered mass-less particle with a specific velocity but according to the electromagnetic theory, a photon is considered to have both energy and momentum. So what happen when they are ...

I have a photon counting system that uses a gated avalanche diode to detect single photons. The repetition frequency of the gates is $f_1$ and the temporal gate width is $\tau_1$ (so the duty cycle is ...

If we describe a photons with a wave packet, moving towards a potential barrier and E smaller than V, there is a finite chance that it will tunnel to the other side. In this process it is likely that ...

How is it possible to achieve waves which are spatially, but not temporally, coherent? Can this be done with a bandpass filter?
Conversely, how is it possible to achieve waves which are temporally, ...

I understand that star is in Plasma state (all nucleus and electrons are not bound to each other and moving around freely)
Photon is emitted when an excited electron moves back to lower orbit.
So in ...

While looking through the questions, a came across a section about black holes. I immediately though; what would happen if an atom is orbiting a black hole and emitted a photon perpendicular to the ...

I'm new to physics and am just going through some of the free online classes at World Science U, and after watching this video on the nature of the speed of light and its constancy, a question came to ...

See, the energy of a photon is given out by $E = pc = hv$ why don't we substitute for $p$ in $E ^2= p^2 c^2 + m^2 c^4$ by putting $p = \gamma mv$ and then get a value for $m$ (which will be $0$ for a ...

In terms of wave-particle duality for, let's say a photon; how would the frequency practically manifest/demonstrate itself? Like, i understand that the frequency is related to the energy a particle ...

Given that there are a finite number of photons that exist in the universe, and the maximum speed of a photon is governed by the speed of light, is it possible that enough people observed an object, ...

How is the image in a mirror created? Are there infinitely many light rays?
My motivation for the question is from image processing.
We work with images as discrete 2D functions, as matrices.
Spatial ...

In discussing this question about propelling a spacecraft with photons and their relativistic momentum, the author asked that I restate my comment as another question.
If photons can really be used ...

If I send a single photon through a usual beam splitter, is there a limit for the beam splitter to work properly related to the photons broadness in frequency or in space?
For example a femto second ...

In Quantum Information we can use photons for quantum bits (qubits). What i often read is that each photon can carry one unit of information, i.e. using the polarization state of a single photon.
I ...

consider a single photon. Since it is not possible to create a photon with a certain frequency it can be characterized by a normalized frequency distribution $f(\nu)$ that is peaked around some mean ...

I am wondering how to describe the collapse of a photon state when it is measured in the polarization degree of freedom (say by a filter which let pass just one particular polarisation).
Let the free ...

I've gotten used to the fact that a spin can be described by its total spin and its $z$-component. And I've learned that a particle (really, anything) with spin 1 forms a triplet with three possible ...

I have always been interested in Physics, and lots of people say that light is a particle and a wave.
How is it possible? How can a photon (a light particle) be a wave as well, when its a particle?
...

I hope lab / experimental physics is fair game for this web-site. If not, sorry!
I'm designing a sensor system to perform specialized [astronomy and space-sciences] experiments, and need a "reality ...

What is the relation between electrons and photons? Why do atoms get excited when their electrons come in contact with photons? Why do electrons go from a higher to lower energy level when emitting a ...